Polyhydroxyalkanoates production by isolates from a polluted salt-lagoon.

Polyhydroxyalkanoates (PHAs) are a family of biodegradable polyesters having a number of possible industrial applications. They are synthesised as intracellular carbon and energy storage material by a wide variety of bacteria. The main obstacle to PHA diffusion is its high production cost greatly depending, among others, upon the cost of the fermentation substrate to be utilised as a carbon source. The use of agricultural waste materials could play an important role in economic production of PHA [1]. Starch or hydrolysed starch, cellulose and hemicellulose along with sucrose and cheese whey have been proposed as economical sources [2]. Polymer production was studied in many bacteria and recently also in moderately halophilic bacteria, which grow optimally with 3-15% (w/v) NaCl [3]. Nevertheless, investigations on the phenotypic characteristics of some type strains belonging to the genus Halomonas has revealed poly(β-hydroxybutyrate) [P(3HB)] accumulation for several species. In contrast to the culture requirements of extremely halophilic archaea, sodium chloride concentrations of 0.5 and 4.5% (w/v) provided the highest cell densities and PHB accumulation in the case of H. boliviensis [4]. The production of P(3HB) by H. boliviensis from hydrolyased starch and from sucrose was also described [5]. The objective of the present work was to isolate from the salt-lagoon of Sottomarina (Venice, Italy) bacteria able to degrade different carbon sources such as glycerol and lactose and producing PHA at the same time. Specially, we worked on the isolation of bacteria growing at 8 % (w/v) NaCl. Some isolates, were identified by 16S rDNA sequence analysis as belonging to the genus Halomonas. Here we report preliminary results on the bacterial conversion of glycerol and lactose to PHA by the selected isolates.